The invention relates to making flow mixers out of ceramic matrix composite (CMC) material for bypass gas turbine aeroengines.
In a bypass gas turbine aeroengine, the incoming air flow admitted through the fan is split into a primary flow that passes through the compressor, the combustion chamber, and the turbine, and a secondary flow or fan flow that bypasses the compressor, the combustion chamber, and the turbine. At the outlet, the “hot” primary flow comprising the combustion gases and the “cold” fan flow are mixed together.
In order to reduce the noise of the ejected jet, it is known to use lobed mixers that encourage mixing between the flows.
Proposals have been made to use CMC material for making such lobe mixers in order to minimize their weight while retaining good mechanical behavior. CMC materials are known for their thermostructural properties, i.e. mechanical properties that enable them to act as structural parts, with the ability to retain these properties at high temperatures. Typical CMC materials comprise fiber reinforcement made of refractory fibers (carbon fibers or ceramic fibers) densified by a matrix that is at least in part ceramic.
A CMC lobed mixer is described in document WO 2006/035186. The mixer described in that document is made up of a plurality of lobed structures in the form of sectors that are made separately out of CMC material and then assembled together, and the mixer is also provided with an internal stiffener ring.